maria hayward
to excessive gas bubbles within the pond, which can lead to problems of embolisms (although this is extremely rare). Excessive algal growth can, conversely, deplete oxygen levels – seemingly paradoxically... During the ‘dark phase’ which (not surprisingly) happens at night, the algae actually release carbon dioxide and consume oxygen! For both of these reasons then, it’s
especially important that ponds suffering from particularly dense algal growth (especially blanketweed), are provided with a sufficient turnover of water in the summer months. This is important not only to adequately turn over the pond during the night when oxygen levels will be at their lowest, but also to help drive off any excessive oxygenation in the daytime, which can also cause problems.
frisky fish During the summer months, the fish may
start to become a little – ahem – frisky, and this can lead to additional water quality problems. For example, the levels of nitrite and ammonia may rise soon after spawning has occurred. It’s advisable to remove any eggs from
the water as they can be a source of infection as they rot (and are far best cultured in
Top tips
• Oxygen levels can vary throughout the day due to a variety of factors, including plant activity. Testing oxygen levels at around 6am will give an indication of the lowest levels of oxygen that the pond will experience throughout the day.
• Koi are actually, to a certain extent anyway, adapted to relatively low oxygen levels, and appear to be able to withstand levels as low as 3mg/l. Sturgeons and sterlets, however, are much more demanding of adequate oxygenation, and it’s absolutely vital that sufficient levels (as close to saturation as possible) are maintained if such fish are kept together with carp.
• Just as we can experience a range of nasty health issues by being exposed to excessive amounts of intense sunlight, so can fish! Ensure that some form of protection is provided from the sun to prevent damage to the integument (skin) of the koi, especially in shallow, very clear ponds. This could be through the planting of, say, lilies, or courtesy of a simple floating platform.
There are several types of thermometer available that allow the koi keeper to monitor the water temperature routinely.
This is a simple floating model.
isolation if this is desired). The use of spawning ropes can help in this respect. It will be necessary to pay very close
attention to the koi following any of their extended ‘love-ins’, as the females especially may be treated extremely roughly by over- amorous males. Finally, it’s worth remembering that a
little bit of hard work during the summer can really pay off for the year ahead. Maintaining optimal water quality is the number one factor promoting the health of koi, and if they are correctly cared for over the summer, they can enter the autumn and winter in the best possible health. This, in turn, allows them to enter spring with a greatly reduced chance of disease.
DAVE WOLFENDEN
Dissolved oxygen should be monitored, especially in hot weather: here an electronic DO tester is being used
Further information:
For more information about Tetra’s products and services go to
www.tetra.net.
A little bit of hard work during the summer can really pay off for the year ahead
JULY 2010 37
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